While sports medicine has gained a deeper understanding of head injuries in recent years, protective headgear hasn't kept pace, and that is particularly true when it comes to bicycle helmets, experts in the field tell CBC News.

Bike helmets were designed to protect against catastrophic head injuries like skull fractures, lacerations or contusions on the brain, which they do.

However, as the understanding of concussions has advanced significantly in recent years, basic helmet design has not, and the standard that North American helmet manufacturers follow has not changed since 1999.

If a cyclist falls and his head hits the pavement or an automobile, the brain could undergo what scientists call linear acceleration – moving in the direction of the impact. And by moderating that, helmets can reduce the risk of skull fractures, neurosurgeon Charles Tator told CBC News.

Tator is a surgeon at Toronto Western Hospital and a professor of neurosurgery at the University of Toronto. He founded ThinkFirst Canada, an injury prevention group, and is now a board member of its successor organization, Parachute Canada.

However, at impact the brain may also undergo rotational or angular acceleration.

"The evidence from science is that concussion is more related to rotational acceleration, which in laymen's terms is really a jiggle of the brain. It's like the movement of Jell-O in a bowl when you jiggle it," Tator explains. And the result of that jiggle can be cellular damage to the brain, which can affect neurons and their connectors.

He says "it is time that our standards include measures of angular acceleration."